The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 19, 1995
Filed:
Mar. 03, 1992
William M Sullivan, Laurel, MS (US);
William W Irwin, Jr, Taylorsville, MS (US);
Charles W Murin, Hattiesburg, MS (US);
James R McNair, Bay Springs, MS (US);
Clifford R Stine, Austin, TX (US);
Sunbeam Corporation, Fort Lauderdale, FL (US);
Abstract
A flexible, electric heating pad having a self-limiting heating element is provided. The heating element includes a pair of relatively spaced conductors surrounded by a positive temperature coefficient (PTC) material. A layer of electrically insulating material surrounds the PTC material. The PTC material includes a polyolefin resin having a relatively low flexural modulus. The heating element is disposed in a generally serpentine configuration within passages formed in the covering material of the heating pad. The passages are formed by joining together layers of covering material using ultrasonic welding or other suitable ways. The temperature of the heating element is controlled using controller circuit which utilizes a solid state timed interval control circuit. A safety circuit is provided for non-resettably disconnecting electrical power from the heating element if short or open circuit conditions occur therein. A temperature indicator and a variable automatic shutoff circuit are also provided with the controller circuit. A method of making the heating pad is also provided.